''Pinus hartwegii'' ( syn. ''P. rudis'', ''P. donnell-smithii''), Hartweg's pine or pino de las alturas, is a

pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. The World Flora Online created by the Royal Botanic Gardens, Kew and Missouri Botanical Garden accep ...

native to the

mountain A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited Summit (topography), summit area, and ...

s of

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

and

Central America Central America ( es, América Central or ) is a subregion of the Americas. Its boundaries are defined as bordering the United States to the north, Colombia to the south, the Caribbean Sea to the east, and the Pacific Ocean to the west. ...

east to

Honduras Honduras, officially the Republic of Honduras, is a country in Central America. The republic of Honduras is bordered to the west by Guatemala, to the southwest by El Salvador, to the southeast by Nicaragua, to the south by the Pacific Oce ...

. It is named after

Karl Theodor Hartweg Karl Theodor Hartweg (18 June 1812 – 3 February 1871) was a German botanist. He collected numerous new species of plants in Colombia, Ecuador, Guatemala, Mexico and California in the United States, collecting for the London Horticultural Society ...

, who described it in 1838.

Distribution

''Pinus hartwegii'' is a very high elevation species, growing at elevations of . It forms the alpine tree line on most of Mexico's higher mountains. It grows on both the

Sierra Madre Occidental The Sierra Madre Occidental is a major mountain range system of the North American Cordillera, that runs northwest–southeast through northwestern and western Mexico, and along the Gulf of California. The Sierra Madre is part of the American C ...

and

Sierra Madre Oriental The Sierra Madre Oriental () is a mountain range in northeastern Mexico. The Sierra Madre Oriental is part of the American Cordillera, a chain of mountain ranges (cordillera) that consists of an almost continuous sequence of mountain ranges that f ...

(mountain ranges) (29° North latitude) from Chihuahua State and

Nuevo León Nuevo León () is a state in the northeast region of Mexico. The state was named after the New Kingdom of León, an administrative territory from the Viceroyalty of New Spain, itself was named after the historic Spanish Kingdom of León. With a ...

(26°) to the highest peaks in the mountain ranges on the

El Salvador El Salvador (; , meaning " The Saviour"), officially the Republic of El Salvador ( es, República de El Salvador), is a country in Central America. It is bordered on the northeast by Honduras, on the northwest by Guatemala, and on the south b ...

—

border (15° North latitude). In the Sierra Madre Occidental this pine grows with very dry winters and a very heavy rainy season in summer, with constant frosts from October to March. This pine does not acquire the dwarfed and contorted shape shared by many species at high elevation. Even at the alpine

tree line The tree line is the edge of the habitat at which trees are capable of growing. It is found at high elevations and high latitudes. Beyond the tree line, trees cannot tolerate the environmental conditions (usually cold temperatures, extreme snowp ...

, this tree is not damaged by the cold and wind-blown ice present at that elevation. Consequently, ''Pinus hartwegii'' has been studied as an evolutionarily unique member on tree line

ecophysiology Ecophysiology (from Greek , ''oikos'', "house(hold)"; , ''physis'', "nature, origin"; and , '' -logia''), environmental physiology or physiological ecology is a biological discipline that studies the response of an organism's physiology to enviro ...

Description

''Pinus hartwegii'' is an

evergreen In botany, an evergreen is a plant which has foliage that remains green and functional through more than one growing season. This also pertains to plants that retain their foliage only in warm climates, and contrasts with deciduous plants, which ...

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...

reaching in height, with a broad, rounded crown. The bark is thick, dark grey-brown, and scaly or fissured. The

leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...

are needle-like, dark green, five (occasionally four) per fascicle, 10–20 cm long and 1.2-1.5 mm thick, the persistent fascicle sheath 1.5–2 cm long. The

cones A cone is a three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the apex or vertex. A cone is formed by a set of line segments, half-lines, or lines conn ...

are ovoid, 6–13 cm long, black or very dark purple, opening when mature in spring to 5–7 cm broad. The

seed A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiospe ...

s are winged, 5–6 mm long with a 1.5-2.5 cm wing. Pollination is in late spring, with the cones maturing 20–22 months after. It is closely related to ''Pinus montezumae'' (Montezuma pine) , differing from it in the shorter leaves, black (not brown) and smaller cones; it replaces Montezuma pine at high elevations, and often hybridises with it where they meet at middle elevations.

References

External links

{{Taxonbar, from=Q136695 hartwegii Trees of Northeastern Mexico Trees of Chiapas Trees of Guerrero Trees of Michoacán Trees of Puebla Trees of Oaxaca Trees of Veracruz Trees of Guatemala Trees of El Salvador Trees of Honduras Trees of Central Mexico Flora of Northeastern Mexico Flora of the Sierra Madre Occidental Flora of the Sierra Madre Oriental Flora of the Trans-Mexican Volcanic Belt Least concern flora of North America